We'll address the character's dialogue voice soon, but basically, it's how the people in your book talk to each other.
A viewpoint voice is a bit different, and you see it most clearly in first-person stories. It's how the character in your book not only talks, but thinks. A few examples:
The best time to talk to ghosts is just before the sun comes up. That's when they can hear us true, Momma said. That's when ghosts can answer us.
The eastern sky was peach colored but a handful of lazy stars still blinked in the west. It was almost time.
"May I run ahead, sir?" I asked.
Pastor Weeks sat at the front of his squeaky wagon with Old Ben next to him, the mules' reins loose in his hands. The pine coffin that held Miss Mary Finch--wearing her best dress, with her hair washed clean and combed-bounced in the back when the wagon wheels hit a rut. My sister, Ruth, sat next to the coffin. Ruth was too big to carry, plus the pastor knew about her peculiar manner of being, so it was the wagon for her and the road for me.
Old Ben looked to the east and gave me a little nod. He knew a few things about ghosts too.
From Chains by Laurie Halse Anderson
The main character in Chains is a young slave girl who lives at the beginning of the Revolutionary War. The main character in the next excerpt is a modern teenager with paranormal powers
"Wait--did you--You just yawned!" The vampire's arms raised over his head in the classic Dracula pose, dropped to his sides. He pulled his exaggerated white fangs back behind his lips. "What, imminent death isn't exciting enough for you?"
"Oh, stop pouting. But really, the widow's peak? The pale skin? The black cape? Where did you even get that thing, a costume store?"
He raised himself to his full height and glared down at me. "I'm going to suck the life from your pretty white neck."
I sighed. I hated the vamp jobs. They think they're so suave. It's not enough for them to slaughter and eat you like a zombie would. No, they want it to be all sexy, too. And, trust me: vampires? Not. Sexy. I mean, sure, their glamours can be pretty hot, but the dry-as-bone corpse bodies shimmering underneath? Nothing attractive there. Not that anyone else can see them though.
From Paranormalcy by Kiersten White
From the first sentence, the first paragraph, you know you're dealing with two completely different narrators.
Both of these passages contain equal amounts of action and internal thought. You can hear the character's voice in the turns of phrase that they use, but you can also see it in the things they notice and how they describe their world. A person who describes a sky as "peach-colored" is a different sort of person than one who uses the phrase "dry-as-bone corpse bodies".
Some character voices have a lot of internal thoughts.
I guess in the old days, in other places, boys like me usually ended up twisting and kicking in the empty air beneath gallows.
It's no wonder I became a monster, too.
I mean, what would you expect, anyway?
And all the guys I know--all the guys I ever knew--can look at their lives and point to the one defining moment that made them who they were, no question about it. Usually those moments involved things like hitting baseballs, or their dads showing them how to gap spark plugs or bait a hook. Stuff like that.
My defining moment came last summer, when I was sixteen.
That's when I got kidnapped.
From The Marbury Lens by Andrew Smith
Or your character's voice can come through without any internal conversation at all.
The match snapped, then sizzled, and I woke up fast. I heard my mother inhale as she took a long pull on a cigarette. Her lips stuck on the filter, so I knew she was still wearing lipstick. She'd been up all night.
She lay on the bed next to me. I felt her fingers on my hair and kept sleep-breathing. I risked a look under my eyelashes.
She was in her pink nightgown, ankles crossed, head flung back against the pillows. Arm in the air, elbow bent, cigarette glowing in her fingers. Tanned legs glistening in the darkness. Blond hair tumbling past her shoulders.
I breathed in smoke and My Sin perfume. It was her smell. It filled the air.
I didn't move, but I could tell she knew I was awake. I kept on pretending to be asleep. She pretended not to know.
I breathed in and out, perfume and smoke, perfume and smoke, and we lay like that for a long time, until i heard the seagulls crying, sadder than a funeral, and I knew it was almost morning.
From What I Saw and How I Lied by Judy Blundell
There are a lot of things that make a character voice memorable, but I'm going to break it into three pieces.
1. Details. Like I said before, a huge part of a character's voice, especially in first person, are the details they notice. The main character in Chains says almost nothing about the landscape (at first), but she does think about the way the woman in the coffin is dressed and how her hair is combed.
Details are also important for a character's mood. When, the main character in What I Saw and How I Lied hears the seagulls crying, she describes it as a sad sound.
2. Language/Slang. The Marbury Lens and Paranormalcy both feature teenagers with modern voices. What I Saw and How I Lied and Chains are both historical novels, one set in the 1940s, the other in the 1700's.
You can tell a bit about the character's setting by the words they use and the rhythm of their sentences. The Marbury Lens and Paranormalcy use modern phrases and informal speech patterns that would sound out of place in either of the other two books.
3. Personality and Concerns. The main character in the Marbury Lens struggles with self-hate and blame. The main character in Paranormalcy is capable, confident and sarcastic. These things play a part in their character voices.
Characters are also defined by what they're concerned about in the moment. The girl in Chains is thinking about ghosts and how she has to walk beside the cart. The girl in What I Saw and How I Lied is thinking about her mother.
What concerns your character, how they think and how they speak all play a part in a character's viewpoint voice.
But how do you develop the ability to write great character voice? Like author voice, the answer is simple. You write and you read.
Reading is very important here. You won't be able to tell when your characters sound bland if you never read books that do characters really well. And it will be even harder for you to know when you've found a good character voice if you don't even know what that means.
I know this is a lot to digest in one post. Did I miss anything? Do you have any questions?
You can find the rest of the voice series here:
Talking about Voice, part 1: What is it?
Talking about Voice, part 2: Three authors, three books
Talking about Voice, part 3: One author, three books
Talking about Voice, part 5: Differences in character dialogue
Talking about Voice, part 6: Helpful links